Background Circulating leptin:adiponectin ratio (L:A) is a potential surrogate marker for cardiometabolic diseases; however, the relationship of the L:A with the occurrence of metabolic syndrome (MetS) has not yet been fully explored in the general Japanese population. Methods We enrolled 678 Japanese subjects (208 men and 470 women, mean age: 58.8±14.4 [SD] yr; mean body mass index: 23.6±3.3 kg/m 2 ) in this study, and determined their MetS status by using the National Cholesterol Education Program-Adult Treatment Panel (NCEP-ATP) recommendations with minor modifications for the Japanese population. Biochemical markers such as leptin and adiponectin present in blood were measured. The statistical analyses performed were gender-based. Results A in subjects with MetS was significantly higher than that in subjects without MetS, regardless of gender. The L:A also showed a significant and gradual increase corresponding to the increase in the number of components of MetS present in both the genders (trend P <0.01). The cut-off level of the L:A to detect MetS was 0.59 (sensitivity: 0.72, specificity: 0.70) in men and 1.04 (sensitivity: 0.72, specificity: 0.69) in women. Conclusions These results suggest that the L:A can serve as a clinically useful marker for detecting MetS characteristics in the general Japanese population. The clinical application of this laboratory index for detecting MetS should be assessed in future studies.